Select Logic in Query. Is this possible in Oracle? - sql

Question

Im trying to implement some sort of logic on the select statement of the query. I want it so that if no attribute is given, or if the inAttribute is 'NONE'; it will return the date and ALL of the values (compprice, compspread,price,spread,run).
If a value was given to in attribute then i want it to return the value it requested for (Refer to the case statement i tried to do).
Below is my attempt at it, and it is just not working. Any help please?
SELECT
mi.date,
IF inAttribute = '' THEN
mi.compprice,
mi.compspread,
mi.price,
mi.spread,
mi.run
ELSE
CASE inAttribute
WHEN 'CP' THEN mi.compprice,
WHEN 'CS THEN mi.compspread,
WHEN 'MP' THEN mi.price,
WHEN 'MS' THEN mi.spread,
WHEN 'R' THEN mi.run
END
END IF
FROM userValueTable mi
WHERE mi.index_family = inIdxFamily
AND mi.index_id = inIdxId
AND mi.date_>= inStartDate
AND mi.date_<= inEndDate
ORDER by mi.date_ ASC;

Answer 1

Few remarks You can't have variable column list from one line to another. '' is equal to NULL, comparing NULL with equality ( = ) is always false. you can have some fixed number of columns and set value of any column using CASE clause.

Answer 2

Oracle doesn't have an IF for SQL. Use CASE instead - it can act like a C/C#/Java/etc switch - case as you have it in your query, and it can also act like an if.
Also, as mentioned above:
You're stuck with returning a constant number of columns unless you use dynamic SQL
In Oracle, '' is treated as NULL so instead of = '' use IS NULL.
If you don't want to go to Dynamic SQL, you could add a "type" column to your select list and then null out any inapplicable values. Your downstream logic could pick the values to use (or ignore) based on the type. Here's an example:
SELECT
mi.date,
CASE
WHEN inAttribute IS NULL THEN 'inAttrNull'
ELSE 'inAttrNotNull'
END AS RecordType,
CASE WHEN inAttribute IS NULL THEN mi.compprice END AS compprice,
CASE WHEN inAttribute IS NULL THEN mi.compspread END AS compspread,
CASE WHEN inAttribute IS NULL THEN mi.price END AS price,
CASE WHEN inAttribute IS NULL THEN mi.spread END AS spread,
CASE WHEN inAttribute IS NULL THEN mi.run END AS run,
CASE inAttribute
WHEN 'CP' THEN mi.compprice
WHEN 'CS' THEN mi.compspread
WHEN 'MP' THEN mi.price
WHEN 'MS' THEN mi.spread
WHEN 'R' THEN mi.run
END AS SpecialValue
FROM userValueTable mi
... and your WHERE and ORDER BY clauses
You'll get a result set something like this:
RecordType compprice compspread price spread run specialvalue
------------- ---------- ---------- ---------- ---------- ---------- ------------
inAttrNotNull (null) (null) (null) (null) (null) 1234.56
inAttrNull 111.11 222.22 333.33 444.44 555.55 (null)
I know this isn't what you wanted, but it may be something you can work with as an alternative.

Answer 3

There is no IF in Oracle SQL, only in PL/SQL. You have to rewrite it to CASE. The same as you did in your query in ELSE part (you missed a single closing quote after 'CS' THEN...).
SELECT ...
(CASE WHEN inAttribute IS NULL THEN mi.compprice
WHEN .... THEN...
WHEN .... THEN...
...
ELSE ...
END) AS some_column_alias
FROM ...